The present invention relates to a printing apparatus for use in a cash register or the like, which has first and second sheets, such as a receipt sheet and a journal sheet, disposed in parallel to each other on a platen and line-feeds these sheets at the time of printing, and more particularly, to an improved printing apparatus for use in a cash register, which sets the timing of line-feeding the receipt sheet in relation to the position of a movable printing body.
For instance, in a printing apparatus for a cash register, a receipt sheet and a journal sheet are provided in parallel to each other in the running direction of a printing head of a movable printing body, a narrow and elongated printing ink ribbon is set laterally over these sheets, and the movable printing body moves reciprocatably along the ribbon. At the time of printing, the movable printing body reciprocatably moves from the receipt sheet to the journal sheet and during this reciprocation, the printing head alternately prints data on the receipt and journal sheets through the ribbon. At this time, in line-feeding the receipt sheet, the receipt sheet moves in its feeding direction by a predetermined line pitch at a timing when the movable printing body returns from one side-edge of the journal sheet to the other side-edge which is adjacent to the receipt sheet.
However, if the line-feeding of the receipt sheet is interrupted by, for example, an operator's hand accidentally touching the upper portion of the receipt sheet while the line-feeding of the receipt sheet is being carried out, the receipt sheet would be bent toward the movable printing body. With this state, when the movable printing body returns to the position to face the receipt sheet, the printing body hits one edge of the receipt sheet. Due to the stress applied at that edge, the receipt sheet would be wrinkled and possibly torn, thus causing undesirable sheet jamming.
Such a problem is likely to occur because the receipt sheet needs to be line-fed to the outside of the printing apparatus so that an operator may accidentally touch the moving sheet to interrupt the line-feeding of the sheet. With respect to the journal sheet, by way of contrast, it is not fed out but is wound up inside the printing apparatus, so that no such problem occurs. Since the movable printing body facing the printing sheet laterally moves at a close distance to the sheet disposed on a platen, if the sheet is separated from the platen, the sheet is likely to come into the running path of the printing head, thus interrupting the movement of the movable printing body.